%0 Journal Article
%T ¦Á-Helix Unwinding as Force Buffer in Spectrins
%J -
%D 2018
%R https://doi.org/10.1021/acsnano.7b08973
%X Spectrins are cytoskeletal proteins located at the inner face of the plasma membrane, making connections between membrane anchors and the actin cortex, and between actin filaments. Spectrins share a common structure forming a bundle of 3 ¦Á-helices and play a major role during cell deformation. Here, we used high-speed force spectroscopy and steered molecular dynamics simulations to understand the mechanical stability of spectrin, revealing a molecular force buffering function. We find that spectrin acts as a soft spring at short extensions (70¨C100 £¿). Under continuous external stretching, its ¦Á-helices unwind, leading to a viscous mechanical response over larger extensions (100¨C300 £¿), represented by a constant-force plateau in force/extension curves. This viscous force buffering emerges from a quasi-equilibrium competition between disruption and re-formation of ¦Á-helical hydrogen bonds. Our results suggest that, in contrast to ¦Â-sheet proteins, which unfold in a catastrophic event, ¦Á-helical spectrins dominantly unwind, providing a viscous force buffer over extensions about 5 times their folded length
%U https://pubs.acs.org/doi/10.1021/acsnano.7b08973